To generalize a CTI technology, to improve the easiness to use, to sum and combine in parallel conventional technologies, and to complement a weak point of Windows capable of easily dealing with it on one screen, in a simplified input/output processing technology for CTI software in a technology field uniting a telephone and a computer.

This CTI software has a basic information file for storing basic information screens, a detail information file for storing detail information screens, a business information file for storing business information screens, a history information file for storing a history information screen, and an information processor capable of simultaneously displaying respective screens by referring to the files and dividing one screen into four, so that all huge customer information can be managed and analyzed on one screen. Various customer data can be integrated with a continuous number adding function.